#12. Chris Pratt in Guardians of the Galaxy

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He lost 65 pounds, but based on this before picture, some of that needed to go…

“Six months seems like a long time unless you’re looking backwards…all you have to do is just a few things everyday and remain consistent, and time will fly just as fast as it flies if you’re working hard or not. If you just cut the crap out of your diet, and if you spend an hour a day doing something physical that will make you sweat, six months will pass by, you will feel better mentally, physically, spiritually — it all is tied together.”

#11. Renée Zellweger in Bridget Jones’s Diary

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In the opposite track from most of these actors, Zellweger had to pack on the pounds – she gained 20 pounds to play the iconic British role. Twice. According to her, it’s not quite as much fun as you’d think, either.

“For two days it’s bliss and then you’re full, OK? And you can then indulge all your fantasies about over-eating.

“Fantasies about non-stop chocolate consumption or your fantasies about ordering the pizza and the spaghetti and the garlic bread.

“Then after a week your glucose levels are going crazy. You’re up and down and all over the place. It doesn’t feel good, and no one wants to hear that, but it’s the truth.”

#10. Jared Leto in Chapter 27

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He gained 67 pounds and put his health at risk for this part.

“Really, it’s a stupid thing to do. I got gout, and my cholesterol went up so fast in such a short time that my doctors wanted to put me on Lipitor, which is for much, much older people. Again, though, a fascinating journey.”

#9. Russell Crowe in Body of Lies

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He gained over 60 pounds, and learned how hard it is to lose it.

“If you want to put on weight, you just elect to live a sedentary life style. Just as soon as you stop actually being active and decide to eat what ever you want, then these two things will combine very quickly.”

#8. Mila Kunis in Black Swan

Everyone knows ballet dancers are thin, but even Mila Kunis had to drop 20 pounds for the role.

“I trained four hours a day, seven days a week, for seven months. I had one day off on my birthday and half a day off for the Emmys and the Golden Globes. On those days my ballet instructor worked with me from 5 am to 11 am, then I went to hair and make-up and on to the awards shows.”

#7. Chris Hemsworth in In the Heart of the Sea

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He’d already lost quite a bit for Blackhat, and dropped an additional 15 pounds for this role.

“That’s all we spoke about. You’ve got 15 burly blokes on the sea and all we talked about was our diet and who’d lost more weight and who’s looking really skinny. It’s ridiculous!”

#6. Jake Gyllenhaal in Nightcrawler

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He lost 30 pounds for the role, and quickly realized that there are more side effects than a trimmer waistline:

“I knew if I was hungry that I was in the right spot. Physically, it showed itself, but chemically and mentally, I think it was even a more fascinating journey. It became a struggle for me.”

#5. Christian Bale in The Machinist

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After losing 63 pounds, Bale nearly disappeared. Which isn’t something he would ever like to do again:

“I have no goal of seeing if I can become invisible one day, eat so little that I disappear. I didn’t take this job because I went, ‘Oh, there’s a physical transformation needed.’ I always go, ‘Damn! There’s a physical transformation needed!'”